The present invention relates to the field of communications, and, in particular, a frame-based communications network for providing voice services utilizing a non-synchronous shared medium LAN integrated with a gateway to a synchronous network.
As computers become more and more cost effective for the everyday consumer and for small businesses, such computers become more plentiful for use within local area environments such as homes, office buildings and the like. For example, within a home a person with a computer in the bedroom, and another in the living room, may want to share common files, utilize a common digital subscriber line (DSL), or otherwise transfer information between the computers. Accordingly, various technologies are being developed for computer interconnection of multiple computers located within such environments. One example of such technologies are the Home Phoneline Network Alliance (HPNA) specifications for local area network (LAN) computer interconnection which utilize existing telephone lines within the local environment for the transmission of data packets between the computers.
FIG. 1a shows in block diagram form a general home networking environment within which the present invention can be implemented. Home network 10 includes existing (installed) plain old telephone service (POTS) wiring 12, network clients 14, the computer port side of modem 16 and fax 18. POTS wiring 12 provides wiring infrastructure used to network multiple clients at a customer premises (e.g., home) 20. POTS wiring 12 can be conventional unshielded twisted pair (UTP) wiring that is generally routed internally in the walls of the customer premises 20 to various locations (e.g., rooms) within the customer premises. Subscriber loop 22 (also called a “local loop”) is a physical wiring link that directly connects an individual customer premises 20 to the Central Office through telephone network interface 24, a demarcation point between the inside and outside of customer premises 20. Of particular importance for residential networks are systems that provide communication between computers as reliably and with as high a data rate as possible. Communication over residential telephone wiring is provided through inventive frame-oriented link, media access and physical layer protocols and implementation techniques associated therewith described herein.
Referring now to FIG. 1b, those skilled in the art can appreciate that home phone-line network configuration 10 can also utilize interface 6010 to provide signals outside customer premises 20. For example, interface 6010 can include a V.90 modem as described above, connected through the central office to an internet service provider. Interface 6010 can include an ADSL modem, a VDSL modem or the like transport interface.
Another desired solution for high speed data communications appears to be cable modem systems. Cable modems are capable of providing data rates as high as 56 Mbps, and is thus suitable for high speed file transfer. In a cable modem system, a headend or cable modem termination system (CMTS) is typically located at a cable company facility and functions as a modem which services a large number subscribers. Each subscriber has a cable modem (CM). Thus, the CMTS facilitates bidirectional communication with any desired one of the plurality of CMs. Referring to FIG. 1c, a hybrid fiber coaxial (HFC) network 1010 facilitates the transmission of data between a headend 1012, which includes at least one CMTS, and a plurality of homes 1014, each of which contains a CM. Such HFC networks are commonly utilized by cable providers to provide Internet access, cable television, pay-per-view and the like to subscribers. Approximately 500 homes 1014 are in electrical communication with each node 1016, 1034 of the HFC network 1010, typically via coaxial cable 1029, 1030, 1031. Amplifiers 1015 facilitate the electrical connection of the more distant homes 1014 to the nodes 1016, 1034 by boosting the electrical signals so as to desirably enhance the signal-to-noise ratio of such communications and by then transmitting the electrical signals over coaxial conductors 1030, 1031. Coaxial conductors 1029 electrically interconnect the homes 1014 with the coaxial conductors 1030, 1031, which extend between amplifiers 1015 and nodes 1016, 1034. Each node 1016, 1034 is electrically connected to a hub 1022, 1024, typically via an optical fiber 1028, 1032. The hubs 1022, 1024 are in communication with the headend 1012, via optical fiber 1020, 1026. Each hub is typically capable of facilitating communication with approximately 20,000 homes 1014. The optical fiber 1020, 1026 extending intermediate the headend 1012 and each hub 1022, 1024 defines a fiber ring which is typically capable of facilitating communication between approximately 100,000 homes 1014 and the headend 1012. The headend 1012 may include video servers, satellite receivers, video modulators, telephone switches and/or Internet routers 1018, as well as the CMTS. The headend 1012 communicates via transmission line 1013, which may be a T1 or T2 line, with the Internet, other headends and/or any other desired device(s) or network.
Given the HPNA environment and the Cable Modem System environment, an opportunity exists for a system provider to integrate each respective environment with voice services. FIG. 1d depicts such an integrated environment. As can be seen in FIG. 1d, a connection point in the home to the telephony world (e.g., the world of video, voice, high speed data network traffic), could be provided to a home user through cable modem 1046 which would include an HPNA transceiver. The cable modem system provider may also wish to accomodate providing telephone service along with high speed data service. A home computer user, rather than using a traditional modem to connect to an internet service provider, would find it convenient to utilize cable modem 1046, taking advantage of the very high speed data service provided by the cable modem. Having a cable modem customer, the cable modem provider may also find it commercially beneficial to offer video feeds, and telephone service over the same cable modem network.
A cable modem having an HPNA V2 transceiver included therein, can readily interface into the home phone line network through the telephone jack within the home. Computers coupled to the home network could then communicate through the cable modem to the outside telephony world as described above. However, telephone service coming from outside the customer premises over the cable modem system would be in a digitized packetized format. It would then proceed over the HPNA network in the same digitized packeting format. If the user, in addition to having computers and the like attached to the HPNA network, wished to have an analog telephone(s) connected to the HPNA, the telephone' (s) analog signal could go through a digital conversion and put the digital information into packets for passing the packets back and forth over the network. The analog telephone signal would need to be sampled and packetized at the appropriate clock rate creating the packet after a certain number of samples. In such an implementation, a mechanism would be needed to discover the timing of the cable modem system and to synchronize the conveyance of information between the telephone, the HPNA network, and the cable modem. Therefore, solutions are needed to deal with voice service issues which may arise in such an integrated Home Phone Line/Cable Modem System environment. The present invention provides such a solution.
In accordance with the present invention, as indicated above, a need exists to effectively deliver voice traffic on the Homenetworking (HPNA V2) network. Of note is the need to get the voice traffic to operate within performance goals within the HPNA V2 network. In particular, issues dealing with an A/D converter sampling circuit clock synchronization on the home network, and issues dealing with packet boundaries and when to take a set of samples and call it a packet for use on the home network, need resolution.
Consider the application of voice data in conjunction with the home network, in general. How data is packaged and how higher layer information is communicated are issues which need to be addressed. When the home has a connection point (e.g., a gateway) to the public telephony systems, video/voice high speed data networks, and a phone service provider wishes to supply phone service along with high speed data, one technique is to provide a cable modem instead of having a traditional modem for connection to an internet service provider (ISP). With the cable modem, a computer can be connected thereto to allow the user to have a very high speed data service. The high speed data service provider may also wish to provide video feeds, phone service over the same network. The cable modem could also contain connection points to allow the phones in the home to be connected to the cable modem, that is, the analog phone signal goes into the cable modem and gets converted to appropriate digital signals for transmission from the cable modem to the public telephony network. U.S. patent application Ser. No. 09/501,850 entitled “Cable Modem System with Sample and Packet Synchronization”, owned by the Assignee of the present application and incorporated herein by reference, describes such a system. When the HPNA V2 system is also employed in the home to provide local area network interconnection for the transfer of digital data, such HPNA system can be connected to the cable modem. In turn, if the analog phone were to be connected to the HPNA V2 system, it cannot be directly attached to the HPNA V2 system. The analog phone signal must go through a digital conversion and be put into packets for passage over the digital-based HPNA V2 and the cable modem systems, i.e., when the cable modem system is connected to the HPNA V2 system, telephone service coming over the cable system is in digitized packetized format. When the telephone is attached to the HPNA V2 network, the telephone can have an HPNA V2 transceiver located therewithin or coupled between the telephone and the HPNA line via a converter. However, when taking the telephone signal and packetizing it at the appropriate clock rate and creating a packet after a certain number of samples to synchronize with the cable modem system network, since the telephone is not directly attached to the cable modem system network, a solution is needed to discover the appropriate timing and process the signals to allow proper synchronization with the cable modem system network. The present invention provides such a solution.